''We probably will get close to some of the really significant Australia-wide records,'' said Aaron Coutts-Smith, New South Wales climate services manager at the Bureau of Meteorology. ''The majority of Australia is suffering from extreme high temperatures.''

Among the records to be challenged is the 40.17 degrees average maximum reached on December 21, 1972.

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The country notched up an average maximum of 39.21 degrees on Wednesday, as measured at more than 700 weather sites. That result was narrowly outside the top 10 days recorded since 1950, Dr Coutts-Smith said.

The new record could be reached at the weekend or on Monday, so prolonged is the hot spell. ''All three days are looking fairly intense with widespread heat,'' he said.

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Also within range could be the highest temperature recorded in Australia, of 50.7 degrees at Oodnadatta, in South Australia, on January 2, 1960. At several places in Western Australia, temperatures reached 47.9 degrees on Thursday.

While a slew of towns in central Australia are tipped to hit 45 degrees or more during the heatwave, ''it's not unheard of for these forecasts to be a little bit out'', Dr Coutts-Smith said. ''We are watching it closely.''

Australia has been warming up for some months, after the start of 2012 was unusually cool at the tail-end of a La Nina climate pattern that brought wet conditions during the past two summers.

The final four months of 2012 saw the hottest average maximum temperatures recorded for the period, the bureau said on Thursday as it released its Annual Australian Climate Statement 2012. Nationally, average maximum temperatures for the September-December period were 1.61 degrees above the 1961-90 average, at 32.47 degrees, narrowly breaking the previous record for the period set in 2002.

The overall figures for last year show the average temperature was 0.11 degrees above the 1961-90 mean of 21.81 degrees.

Rainfall averaged 476 millimetres, compared with a 465-millimetre mean for the 1961-1990 period - well down from the 699 millimetres recorded in 2011.

Within the year, though, Australia saw a big shift as both hotter and drier conditions set in. For example, while the January-March rainfall levels were 32 per cent above average, they slumped to 25 per cent below the norm for the April-December period.

''Are we going back to sort of average years after a La Nina event or are we going back to those dry conditions that really characterised the southern Murray-Darling Basin?'', Karl Braganza, manager of climate monitoring at the Bureau of Meteorology, said.

''Based on the evidence we've seen, we are going back to drier-than-average conditions.''

The British Meteorological Office last month predicted 2013 would be among the hottest for the world on record, with more emissions of greenhouse gases a key factor.

Australian forecasters are reluctant to estimate how 2013 will turn out for the country, mostly because of uncertainty about the balance between La Nina and El Nino climate patterns over the Pacific Ocean. El Nino conditions typically mean hotter and drier weather for much of the country.

''2009 was a really warm year, and that's the last time we had these really warm air masses moving over the continent from quite early on [in the summer],'' Dr Braganza said.

Even after this heatwave subsides, Australians shouldn't expect much respite from a long, hot summer.

''Odds are in favour of hotter and drier conditions to the end of March,'' Dr Braganza said.